Methods of characterizing a component of a polycrystalline diamond compact by at least one magnetic measurement

ABSTRACT

In an embodiment, a method of characterizing a polycrystalline diamond compact is disclosed. The method includes providing the polycrystalline diamond compact, and measuring at least one magnetic characteristic of a component of the polycrystalline diamond compact.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/785,014 filed on 21 May 2010, which is a continuation of U.S. patentapplication Ser. No. 12/244,960 filed on 3 Oct. 2008 (now U.S. Pat. No.7,866,418 issued on 11 Jan. 2011), the disclosure of each of theforegoing applications is incorporated herein, in its entirety, by thisreference.

BACKGROUND

Wear-resistant, superabrasive compacts are utilized in a variety ofmechanical applications. For example, polycrystalline diamond compacts(“PDCs”) are used in drilling tools (e.g., cutting elements, gagetrimmers, etc.), machining equipment, bearing apparatuses, wire-drawingmachinery, and in other mechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller-cone drill bits and fixed-cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly referred to as a diamond table. The diamond table may beformed and bonded to a substrate using a high-pressure, high-temperature(“HPHT”) process. The PDC cutting element may also be brazed directlyinto a preformed pocket, socket, or other receptacle formed in the bitbody. The substrate may often be brazed or otherwise joined to anattachment member, such as a cylindrical backing A rotary drill bittypically includes a number of PDC cutting elements affixed to the bitbody. It is also known that a stud carrying the PDC may be used as a PDCcutting element when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container with a volume of diamond particles positionedadjacent to the cemented carbide substrate. A number of such cartridgesmay be loaded into an HPHT press. The substrates and volume of diamondparticles are then processed under HPHT conditions in the presence of acatalyst material that causes the diamond particles to bond to oneanother to form a matrix of bonded diamond grains defining apolycrystalline diamond (“PCD”) table that is bonded to the substrate.The catalyst material is often a metal-solvent catalyst (e.g., cobalt,nickel, iron, or alloys thereof) that is used for promoting intergrowthof the diamond particles.

In one conventional approach, a constituent of the cemented carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a catalyst topromote intergrowth between the diamond particles, which results information of bonded diamond grains. Often, a solvent catalyst may bemixed with the diamond particles prior to subjecting the diamondparticles and substrate to the HPHT process.

The presence of the solvent catalyst in the PCD table is believed toreduce the thermal stability of the PCD table at elevated temperatures.For example, the difference in thermal expansion coefficient between thediamond grains and the solvent catalyst is believed to lead to chippingor cracking of the PCD table during drilling or cutting operations,which can degrade the mechanical properties of the PCD table or causefailure. Additionally, some of the diamond grains can undergo a chemicalbreakdown or back-conversion to graphite via interaction with thesolvent catalyst. At elevated high temperatures, portions of the diamondgrains may transform to carbon monoxide, carbon dioxide, graphite, orcombinations thereof, thus degrading the mechanical properties of thePDC.

One conventional approach for improving the thermal stability of a PDCis to at least partially remove the solvent catalyst from the PCD tableof the PDC by acid leaching. However, removing the solvent catalyst fromthe PCD table can be relatively time consuming for high-volumemanufacturing. Additionally, depleting the solvent catalyst may decreasethe mechanical strength of the PCD table.

Despite the availability of a number of different PCD materials,manufacturers and users of PCD materials continue to seek PCD materialsthat exhibit improved mechanical and/or thermal properties.

SUMMARY

Embodiments of the invention relate to PCD exhibiting enhanceddiamond-to-diamond bonding. In an embodiment, PCD includes a pluralityof diamond grains defining a plurality of interstitial regions. Ametal-solvent catalyst occupies the plurality of interstitial regions.The plurality of diamond grains and the metal-solvent catalystcollectively may exhibit a coercivity of about 115 Oersteds (“Oe”) ormore and a specific magnetic saturation of about 15 Gauss·cm3/grams(“G·cm3/g”) or less.

In an embodiment, PCD includes a plurality of diamond grains defining aplurality of interstitial regions. A metal-solvent catalyst occupies theplurality of interstitial regions. The plurality of diamond grains andthe metal-solvent catalyst collectively may exhibit a specific magneticsaturation of about 15 G·cm3/g or less. The plurality of diamond grainsand the metal-solvent catalyst define a volume of at least about 0.050cm3.

In an embodiment, a PDC includes a PCD table bonded to a substrate. Atleast a portion of the PCD table may comprise any of the PCD embodimentsdisclosed herein.

In an embodiment, a method includes enclosing a plurality of diamondparticles that exhibit an average particle size of about 30 μm or lessand a metal-solvent catalyst in a pressure transmitting medium to form acell assembly. The method further includes subjecting the cell assemblyto a temperature of at least about 1000° C. and a pressure in thepressure transmitting medium of at least about 7.5 GPa to form PCD.

Further embodiments relate to applications utilizing the disclosed PCDand PDCs in various articles and apparatuses, such as rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical elements or features indifferent views or embodiments shown in the drawings.

FIG. 1A is a schematic diagram of an example of a magnetic saturationapparatus configured to magnetize a PCD sample approximately tosaturation.

FIG. 1B is a schematic diagram of an example of a magnetic saturationmeasurement apparatus configured to measure a saturation magnetizationof a PCD sample.

FIG. 2 is a schematic diagram of an example of a coercivity measurementapparatus configured to determine a coercivity of a PCD sample.

FIG. 3A is a cross-sectional view of an embodiment of a PDC including aPCD table formed from any of the PCD embodiments disclosed herein.

FIG. 3B is a graph illustrating residual principal stress versussubstrate thickness that was measured in a PCD table of a PDC fabricatedat a pressure above about 7.5 GPa and a PCD table of a conventionallyformed PDC.

FIG. 4 is a schematic illustration of a method of fabricating the PDCshown in FIG. 3A.

FIG. 5A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 5B is a top elevation view of the rotary drill bit shown in FIG.5A.

FIG. 6 is an isometric cut-away view of an embodiment of athrust-bearing apparatus that may utilize one or more of the disclosedPDC embodiments.

FIG. 7 is an isometric cut-away view of an embodiment of a radialbearing apparatus that may utilize one or more of the disclosed PDCembodiments.

FIG. 8 is a schematic isometric cut-away view of an embodiment of asubterranean drilling system including the thrust-bearing apparatusshown in FIG. 6.

FIG. 9 is a side cross-sectional view of an embodiment of a wire-drawingdie that employs a PDC fabricated in accordance with the principlesdescribed herein.

DETAILED DESCRIPTION

Embodiments of the invention relate to PCD that exhibits enhanceddiamond-to-diamond bonding. It is currently believed by the inventorsthat as the sintering pressure employed during the HPHT process used tofabricate such PCD is moved further into the diamond-stable region awayfrom the graphite-diamond equilibrium line, the rate of nucleation andgrowth of diamond increases. Such increased nucleation and growth ofdiamond between diamond particles (for a given diamond particleformulation) may result in PCD being formed exhibiting a relativelylower metal-solvent catalyst content, a higher coercivity, a lowerspecific magnetic saturation, and/or a lower specific permeability(i.e., the ratio of specific magnetic saturation to coercivity) than PCDformed at a lower sintering pressure. Embodiments also relate to PDCshaving a PCD table comprising such PCD, methods of fabricating such PCDand PDCs, and applications for such PCD and PDCs in rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

PCD Embodiments

According to various embodiments, PCD sintered at a pressure of at leastabout 7.5 GPa may exhibit a coercivity of 115 Oe or more, a high-degreeof diamond-to-diamond bonding, a specific magnetic saturation of about15 G·cm³/g or less, and a metal-solvent catalyst content of about 7.5weight % (“wt %”) or less. The PCD includes a plurality of diamondgrains directly bonded together via diamond-to-diamond bonding to definea plurality of interstitial regions. At least a portion of theinterstitial regions or, in some embodiments, substantially all of theinterstitial regions may be occupied by a metal-solvent catalyst, suchas iron, nickel, cobalt, or alloys of any of the foregoing metals. Forexample, the metal-solvent catalyst may be a cobalt-based materialincluding at least 50 wt % cobalt, such as a cobalt alloy.

The diamond grains may exhibit an average grain size of about 50 μm orless, such as about 30 μm or less or about 20 μm or less. For example,the average grain size of the diamond grains may be about 10 μm to about18 μm and, in some embodiments, about 15 μm to about 18 μm. In someembodiments, the average grain size of the diamond grains may be about10 μm or less, such as about 2 μm to about 5 μm or submicron. Thediamond grain size distribution of the diamond grains may exhibit asingle mode, or may be a bimodal or greater grain size distribution.

The metal-solvent catalyst that occupies the interstitial regions may bepresent in the PCD in an amount of about 7.5 wt % or less. In someembodiments, the metal-solvent catalyst may be present in the PCD in anamount of about 3 wt % to about 7.5 wt %, such as about 3 wt % to about6 wt %. In other embodiments, the metal-solvent catalyst content may bepresent in the PCD in an amount less than about 3 wt %, such as about 1wt % to about 3 wt % or a residual amount to about 1 wt %. Bymaintaining the metal-solvent catalyst content below about 7.5 wt %, thePCD may exhibit a desirable level of thermal stability suitable forsubterranean drilling applications.

Many physical characteristics of the PCD may be determined by measuringcertain magnetic properties of the PCD because the metal-solventcatalyst may be ferromagnetic. The amount of the metal-solvent catalystpresent in the PCD may be correlated with the measured specific magneticsaturation of the PCD. A relatively larger specific magnetic saturationindicates relatively more metal-solvent catalyst in the PCD.

The mean free path between neighboring diamond grains of the PCD may becorrelated with the measured coercivity of the PCD. A relatively largecoercivity indicates a relatively smaller mean free path. The mean freepath is representative of the average distance between neighboringdiamond grains of the PCD, and thus may be indicative of the extent ofdiamond-to-diamond bonding in the PCD. A relatively smaller mean freepath, in well-sintered PCD, may indicate relatively morediamond-to-diamond bonding.

As merely one example, ASTM B886-03 (2008) provides a suitable standardfor measuring the specific magnetic saturation and ASTM B887-03 (2008)e1 provides a suitable standard for measuring the coercivity of the PCD.Although both ASTM B886-03 (2008) and ASTM B887-03 (2008) e1 aredirected to standards for measuring magnetic properties of cementedcarbide materials, either standard may be used to determine the magneticproperties of PCD. A KOERZIMAT CS 1.096 instrument (commerciallyavailable from Foerster Instruments of Pittsburgh, Pa.) is one suitableinstrument that may be used to measure the specific magnetic saturationand the coercivity of the PCD.

Generally, as the sintering pressure that is used to form the PCDincreases, the coercivity may increase and the magnetic saturation maydecrease. The PCD defined collectively by the bonded diamond grains andthe metal-solvent catalyst may exhibit a coercivity of about 115 Oe ormore and a metal-solvent catalyst content of less than about 7.5 wt % asindicated by a specific magnetic saturation of about 15 G·cm3/g or less.In a more detailed embodiment, the coercivity of the PCD may be about115 Oe to about 250 Oe and the specific magnetic saturation of the PCDmay be greater than 0 G·cm3/g to about 15 G·cm3/g. In an even moredetailed embodiment, the coercivity of the PCD may be about 115 Oe toabout 175 Oe and the specific magnetic saturation of the PCD may beabout 5 G·cm3/g to about 15 G·cm3/g. In yet an even more detailedembodiment, the coercivity of the PCD may be about 155 Oe to about 175Oe and the specific magnetic saturation of the PCD may be about 10G·cm3/g to about 15 G·cm3/g. The specific permeability (i.e., the ratioof specific magnetic saturation to coercivity) of the PCD may be about0.10 or less, such as about 0.060 to about 0.090. Despite the averagegrain size of the bonded diamond grains being less than about 30 μm, themetal-solvent catalyst content in the PCD may be less than about 7.5 wt% resulting in a desirable thermal stability.

In one embodiment, diamond particles having an average particle size ofabout 18 μm to about 20 μm are positioned adjacent to a cobalt-cementedtungsten carbide substrate and subjected to an HPHT process at atemperature of about 1390° C. to about 1430° C. and a pressure of about7.8 GPa to about 8.5 GPa. The PCD so-formed as a PCD table bonded to thesubstrate may exhibit a coercivity of about 155 Oe to about 175 Oe, aspecific magnetic saturation of about 10 G·cm3/g to about 15 G·cm3/g,and a cobalt content of about 5 wt % to about 7.5 wt %.

In one or more embodiments, a specific magnetic saturation constant forthe metal-solvent catalyst in the PCD may be about 185 G·cm3/g to about215 G·cm3/g. For example, the specific magnetic saturation constant forthe metal-solvent catalyst in the PCD may be about 195 G·cm3/g to about205 G·cm3/g. It is noted that the specific magnetic saturation constantfor the metal-solvent catalyst in the PCD may be composition dependent.

Generally, as the sintering pressure is increased above 7.5 GPa, a wearresistance of the PCD so-formed may increase. For example, the Gratiomay be at least about 4.0×106, such as about 5.0×106 to about 15.0×10 6or, more particularly, about 8.0×106 to about 15.0×106. In someembodiments, the Gratio may be at least about 30.0×106. The Gratio isthe ratio of the volume of workpiece cut to the volume of PCD worn awayduring the cutting process. An example of suitable parameters that maybe used to determine a Gratio of the PCD are a depth of cut for the PCDcutting element of about 0.254 mm, a back rake angle for the PCD cuttingelement of about 20 degrees, an in-feed for the PCD cutting element ofabout 6.35 mm/rev, a rotary speed of the workpiece to be cut of about101 rpm, and the workpiece may be made from Barre granite having a 914mm outer diameter and a 254 mm inner diameter. During the Gratio test,the workpiece is cooled with a coolant, such as water.

In addition to the aforementioned Gratio, despite the presence of themetal-solvent catalyst in the PCD, the PCD may exhibit a thermalstability that is close to, substantially the same as, or greater than apartially leached PCD material formed by sintering a substantiallysimilar diamond particle formulation at a lower sintering pressure(e.g., up to about 5.5 GPa) and in which the metal-solvent catalyst(e.g., cobalt) is leached therefrom to a depth of about 60 μm to about100 μm from a working surface. The thermal stability of the PCD may beevaluated by measuring the distance cut in a workpiece prior tocatastrophic failure, without using coolant, in a vertical lathe test(e.g., vertical turret lathe or a vertical boring mill). An example ofsuitable parameters that may be used to determine thermal stability ofthe PCD are a depth of cut for the PCD cutting element of about 1.27 mm,a back rake angle for the PCD cutting element of about 20 degrees, anin-feed for the PCD cutting element of about 1.524 mm/rev, a cuttingspeed of the workpiece to be cut of about 1.78 msec, and the workpiecemay be made from Barre granite having a 914 mm outer diameter and a 254mm inner diameter. In an embodiment, the distance cut in a workpieceprior to catastrophic failure as measured in the above-describedvertical lathe test may be at least about 1300 m, such as about 1300 mto about 3950 m.

PCD formed by sintering diamond particles having the same diamondparticle size distribution as a PCD embodiment of the invention, butsintered at a pressure of, for example, up to about 5.5 GPa and attemperatures in which diamond is stable may exhibit a coercivity ofabout 100 Oe or less and/or a specific magnetic saturation of about 16G·cm3/g or more. Thus, in one or more embodiments of the invention, PCDexhibits a metal-solvent catalyst content of less than 7.5 wt % and agreater amount of diamond-to-diamond bonding between diamond grains thanthat of a PCD sintered at a lower pressure, but with the same precursordiamond particle size distribution and catalyst.

It is currently believed by the inventors that forming the PCD bysintering diamond particles at a pressure of at least about 7.5 GPa maypromote nucleation and growth of diamond between the diamond particlesbeing sintered so that the volume of the interstitial regions of the PCDso-formed is decreased compared to the volume of interstitial regions ifthe same diamond particle distribution was sintered at a pressure of,for example, up to about 5.5 GPa and at temperatures where diamond isstable. For example, the diamond may nucleate and grow from carbonprovided by dissolved carbon in metal-solvent catalyst (e.g., liquefiedcobalt) infiltrating into the diamond particles being sintered,partially graphitized diamond particles, carbon from a substrate, carbonfrom another source (e.g., graphite particles and/or fullerenes mixedwith the diamond particles), or combinations of the foregoing. Thisnucleation and growth of diamond in combination with the sinteringpressure of at least about 7.5 GPa may contribute to PCD so-formedhaving a metal-solvent catalyst content of less than about 7.5 wt %.

FIGS. 1A, 1B, and 2 schematically illustrate the manner in which thespecific magnetic saturation and the coercivity of the PCD may bedetermined using an apparatus, such as the KOERZIMAT CS 1.096instrument. FIG. 1A is a schematic diagram of an example of a magneticsaturation apparatus 100 configured to magnetize a PCD sample tosaturation. The magnetic saturation apparatus 100 includes a saturationmagnet 102 of sufficient strength to magnetize a PCD sample 104 tosaturation. The saturation magnet 102 may be a permanent magnet or anelectromagnet. In the illustrated embodiment, the saturation magnet 102is a permanent magnet that defines an air gap 106, and the PCD sample104 may be positioned on a sample holder 108 within the air gap 106.When the PCD sample 104 is light-weight, it may be secured to the sampleholder 108 using, for example, double-sided tape or other adhesive sothat the PCD sample 104 does not move responsive to the magnetic fieldfrom the saturation magnet 102 and the PCD sample 104 is magnetizedapproximately to saturation.

Referring to the schematic diagram of FIG. 1B, after magnetizing the PCDsample 104 approximately to saturation using the magnetic saturationapparatus 100, a magnetic saturation of the PCD sample 104 may bemeasured using a magnetic saturation measurement apparatus 120. Themagnetic saturation measurement apparatus 120 includes a Helmholtzmeasuring coil 122 defining a passageway dimensioned so that themagnetized PCD sample 104 may be positioned therein on a sample holder124. Once positioned in the passageway, the sample holder 124 supportingthe magnetized PCD sample 104 may be moved axially along an axisdirection 126 to induce a current in the Helmholtz measuring coil 122.Measurement electronics 128 are coupled to the Helmholtz measuring coil122 and configured to calculate the magnetic saturation based upon themeasured current passing through the Helmholtz measuring coil 122. Themeasurement electronics 128 may also be configured to calculate a weightpercentage of magnetic material in the PCD sample 104 when thecomposition and magnetic characteristics of the metal-solvent catalystin the PCD sample 104 are known, such as with iron, nickel, cobalt, andalloys thereof. Specific magnetic saturation may be calculated basedupon the calculated magnetic saturation and the measured weight of thePCD sample 104.

The amount of metal-solvent catalyst in the PCD sample 104 may bedetermined using a number of different analytical techniques. Forexample, energy dispersive spectroscopy (e.g., EDAX), wavelengthdispersive x-ray spectroscopy (e.g., WDX), and/or Rutherfordbackscattering spectroscopy may be employed to determine the amount ofmetal-solvent catalyst in the PCD sample 104.

If desired, a specific magnetic saturation constant of the metal-solventcatalyst content in the PCD sample 104 may be determined using aniterative approach. A value for the specific magnetic saturationconstant of the metal-solvent catalyst in the PCD sample 104 may beiteratively chosen until a metal-solvent catalyst content calculated bythe analysis software of the KOERZIMAT CS 1.096 instrument using thechosen value substantially matches the metal-solvent catalyst contentdetermined via an analytical technique, such as energy dispersivespectroscopy, wavelength dispersive x-ray spectroscopy, and/orRutherford backscattering spectroscopy.

FIG. 2 is a schematic diagram of a coercivity measurement apparatus 200configured to determine a coercivity of a PCD sample. The coercivitymeasurement apparatus 200 includes a coil 202 and measurementelectronics 204 coupled to the coil 202. The measurement electronics 204are configured to pass a current through the coil 202 so that a magneticfield is generated. A sample holder 206 having a PCD sample 208 thereonmay be positioned within the coil 202. A magnetization sensor 210configured to measure a magnetization of the PCD sample 208 may becoupled to the measurement electronics 204 and positioned in proximityto the PCD sample 208.

During testing, the magnetic field generated by the coil 202 magnetizesthe PCD sample 208 approximately to saturation. Then, the measurementelectronics 204 apply a current so that the magnetic field generated bythe coil 202 is increasingly reversed. The magnetization sensor 210measures a magnetization of the PCD sample 208 resulting fromapplication of the reversed magnetic field to the PCD sample 208. Themeasurement electronics 204 determine the coercivity of the PCD sample208, which is a measurement of the reverse magnetic field at which themagnetization of the PCD sample 208 is zero.

Embodiments of Methods for Fabricating PCD

The PCD may be formed by sintering a mass of a plurality of diamondparticles in the presence of a metal-solvent catalyst. The diamondparticles may exhibit an average particle size of about 50 μm or less,such as about 30 μm or less, about 20 μm or less, about 10 μm to about18 μm, or about 15 μm to about 18 μm. In some embodiments, the averageparticle size of the diamond particles may be about 10 μm or less, suchas about 2 μm to about 5 μm or submicron.

In an embodiment, the diamond particles of the mass of diamond particlesmay comprise a relatively larger size and at least one relativelysmaller size. As used herein, the phrases “relatively larger” and“relatively smaller” refer to particle sizes (by any suitable method)that differ by at least a factor of two (e.g., 30 μm and 15 μm).According to various embodiments, the mass of diamond particles mayinclude a portion exhibiting a relatively larger size (e.g., 30 μm, 20μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at leastone relatively smaller size (e.g., 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm,0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In one embodiment,the mass of diamond particles may include a portion exhibiting arelatively larger size between about 10 μm and about 40 μm and anotherportion exhibiting a relatively smaller size between about 1 μm and 4μm. In some embodiments, the mass of diamond particles may comprisethree or more different sizes (e.g., one relatively larger size and twoor more relatively smaller sizes), without limitation.

It is noted that the as-sintered diamond grain size may differ from theaverage particle size of the mass of diamond particles prior tosintering due to a variety of different physical processes, such asgrain growth, diamond particles fracturing, carbon provided from anothercarbon source (e.g., dissolved carbon in the metal-solvent catalyst), orcombinations of the foregoing. The metal-solvent catalyst (e.g., iron,nickel, cobalt, or alloys thereof) may be provided in particulate formmixed with the diamond particles, as a thin foil or plate placedadjacent to the mass of diamond particles, from a cemented carbidesubstrate including a metal-solvent catalyst, or combinations of theforegoing.

In order to efficiently sinter the mass of diamond particles, the massmay be enclosed in a pressure transmitting medium, such as a refractorymetal can, graphite structure, pyrophyllite, and/or other suitablepressure transmitting structure to form a cell assembly. Examples ofsuitable gasket materials and cell structures for use in manufacturingPCD are disclosed in U.S. Pat. No. 6,338,754 and U.S. patent applicationSer. No. 11/545,929, each of which is incorporated herein, in itsentirety, by this reference. Another example of a suitable pressuretransmitting material is pyrophyllite, which is commercially availablefrom Wonderstone Ltd. of South Africa. The cell assembly, including thepressure transmitting medium and mass of diamond particles therein, issubjected to an HPHT process using an ultra-high pressure press at atemperature of at least about 1000° C. (e.g., about 1100° C. to about2200° C., or about 1200° C. to about 1450° C.) and a pressure in thepressure transmitting medium of at least about 7.5 GPa (e.g., about 7.5GPa to about 15 GPa) for a time sufficient to sinter the diamondparticles together in the presence of the metal-solvent catalyst andform the PCD comprising bonded diamond grains defining interstitialregions occupied by the metal-solvent catalyst. For example, thepressure in the pressure transmitting medium employed in the HPHTprocess may be at least about 8.0 GPa, at least about 9.0 GPa, at leastabout 10.0 GPa, at least about 11.0 GPa, at least about 12.0 GPa, or atleast about 14 GPa.

The pressure values employed in the HPHT processes disclosed hereinrefer to the pressure in the pressure transmitting medium at roomtemperature (e.g., about 25° C.) with application of pressure using anultra-high pressure press and not the pressure applied to exterior ofthe cell assembly. The actual pressure in the pressure transmittingmedium at sintering temperature may be slightly higher. The ultra-highpressure press may be calibrated at room temperature by embedding atleast one calibration material that changes structure at a knownpressure, such as PbTe, thallium, barium, or bismuth in the pressuretransmitting medium. Further, optionally, a change in resistance may bemeasured across the at least one calibration material due to a phasechange thereof. For example, PbTe exhibits a phase change at roomtemperature at about 6.0 GPa and bismuth exhibits a phase change at roomtemperature at about 7.7 GPa. Examples of suitable pressure calibrationtechniques are disclosed in G. Rousse, S. Klotz, A. M. Saitta, J.Rodriguez-Carvajal, M. I. McMahon, B. Couzinet, and M. Mezouar,“Structure of the Intermediate Phase of PbTe at High Pressure,” PhysicalReview B: Condensed Matter and Materials Physics, 71, 224116 (2005) andD. L. Decker, W. A. Bassett, L. Merrill, H. T. Hall, and J. D. Barnett,“High-Pressure Calibration: A Critical Review,” J. Phys. Chem. Ref.Data, 1, 3 (1972).

In an embodiment, a pressure of at least about 7.5 GPa in the pressuretransmitting medium may be generated by applying pressure to a cubichigh-pressure cell assembly that encloses the mass of diamond particlesto be sintered using anvils, with each anvil applying pressure to adifferent face of the cubic high-pressure assembly. In such anembodiment, a surface area of each anvil face of the anvils may beselectively dimensioned to facilitate application of pressure of atleast about 7.5 GPa to the mass of diamond particles being sintered. Forexample, the surface area of each anvil may be less than about 12.0 cm²,such as about 8 cm² to about 10 cm². The anvils may be made from acobalt-cemented tungsten carbide or other material having a sufficientcompressive strength to help reduce damage thereto through repetitiveuse in a high-volume commercial manufacturing environment. Optionally,as an alternative to or in addition to selectively dimensioning thesurface area of each anvil face, two or more internal anvils may beembedded in the cubic high-pressure cell assembly to further intensifypressure. For example, the article W. Utsumi, N. Toyama, S. Endo and F.E. Fujita, “X-ray diffraction under ultrahigh pressure generated withsintered diamond anvils,” J. Appl. Phys., 60, 2201 (1986) isincorporated herein, in its entirety, by this reference and disclosesthat sintered diamond anvils may be embedded in a cubic pressuretransmitting medium for intensifying the pressure applied by anultra-high pressure press to a workpiece also embedded in the cubicpressure transmitting medium.

PDC Embodiments and Methods of Fabricating PDCs

Referring to FIG. 3A, the PCD embodiments may be employed in a PDC forcutting applications, bearing applications, or many other applications.FIG. 3A is a cross-sectional view of an embodiment of a PDC 300. The PDC300 includes a substrate 302 bonded to a PCD table 304. The PCD table304 may be formed of PCD in accordance with any of the PCD embodimentsdisclosed herein. The PCD table 304 exhibits at least one workingsurface 306 and at least one lateral dimension “d” (e.g., a diameter).Although FIG. 1 shows the working surface 306 as substantially planar,the working surface 306 may be concave, convex, or another nonplanargeometry. The substrate 302 may be generally cylindrical or anotherselected configuration, without limitation. Although FIG. 1 shows aninterfacial surface 308 of the substrate 302 as being substantiallyplanar, the interfacial surface 308 may exhibit a selected nonplanartopography, such as a grooved, ridged, or other nonplanar interfacialsurface. The substrate 302 may include, without limitation, cementedcarbides, such as tungsten carbide, titanium carbide, chromium carbide,niobium carbide, tantalum carbide, vanadium carbide, or combinationsthereof cemented with iron, nickel, cobalt, or alloys thereof. Forexample, in one embodiment, the substrate 302 comprises cobalt-cementedtungsten carbide.

FIG. 4 is a schematic illustration of an embodiment of a method forfabricating the PDC 300 shown in FIG. 3A. Referring to FIG. 4, a mass ofdiamond particles 400 having any of the above-mentioned average particlesizes and distributions (e.g., an average particle size of about 50 μmor less) is positioned adjacent to the interfacial surface 308 of thesubstrate 302. As previously discussed, the substrate 302 may include ametal-solvent catalyst. The mass of diamond particles 400 and substrate302 may be subjected to an HPHT process using conditions previouslydescribed with respect to sintering the PCD embodiments disclosedherein. The PDC 300 so-formed includes the PCD table 304 that comprisesPCD, formed of any of the PCD embodiments disclosed herein, integrallyformed with the substrate 302 and bonded to the interfacial surface 308of the substrate 302. If the substrate 302 includes a metal-solventcatalyst, the metal-solvent catalyst may liquefy and infiltrate the massof diamond particles 400 to promote growth between adjacent diamondparticles of the mass of diamond particles 400 to form the PCD table 304comprised of a body of bonded diamond grains having the infiltratedmetal-solvent catalyst interstitially disposed between bonded diamondgrains. For example, if the substrate 302 is a cobalt-cemented tungstencarbide substrate, cobalt from the substrate 302 may be liquefied andinfiltrate the mass of diamond particles 400 to catalyze formation ofthe PCD table 304.

Employing selectively dimensioned anvil faces and/or internal anvils inthe ultra-high pressure press used to process the mass of diamondparticles 400 and substrate 302 enables forming the at least one lateraldimension “d” of the PCD table 304 to be about 0.80 cm or more.Referring again to FIG. 3A, for example, the at least one lateraldimension “d” may be about 0.80 cm to about 3.0 cm and, in someembodiments, about 1.3 cm to about 1.9 cm or about 1.6 cm to about 1.9cm. A representative volume of the PCD table 304 (or any PCD article ofmanufacture disclosed herein) formed using the selectively dimensionedanvil faces and/or internal anvils may be at least about 0.050 cm³. Forexample, the volume may be about 0.25 cm³ to at least about 1.25 cm³ orabout 0.1 cm³ to at least about 0.70 cm³. A representative volume forthe PDC 300 may be about 0.4 cm³ to at least about 4.6 cm³, such asabout 1.1 cm³ to at least about 2.3 cm³.

In other embodiments, a PCD table according to an embodiment may beseparately formed using an HPHT sintering process and, subsequently,bonded to the interfacial surface 308 of the substrate 302 by brazing,using a separate HPHT bonding process, or any other suitable joiningtechnique, without limitation. In yet another embodiment, a substratemay be formed by depositing a binderless carbide (e.g., tungstencarbide) via chemical vapor deposition onto the separately formed PCDtable.

In any of the embodiments disclosed herein, substantially all or aselected portion of the metal-solvent catalyst may be removed (e.g., vialeaching) from the PCD table. In an embodiment, metal-solvent catalystin the PCD table may be removed to a selected depth from at least oneexterior working surface (e.g., the working surface 306 and/or asidewall working surface of the PCD table 304) so that only a portion ofthe interstitial regions are occupied by metal-solvent catalyst. Forexample, substantially all or a selected portion of the metal-solventcatalyst may be removed from the PCD table 304 so-formed in the PDC 300to a selected depth from the working surface 306.

In another embodiment, a PCD table may be fabricated according to any ofthe disclosed embodiments in a first HPHT process, leached to removesubstantially all of the metal-solvent catalyst from the interstitialregions between the bonded diamond grains, and subsequently bonded to asubstrate in a second HPHT process. In the second HPHT process, aninfiltrant from, for example, a cemented carbide substrate mayinfiltrate into the interstitial regions from which the metal-solventcatalyst was depleted. For example, the infiltrant may be cobalt that isswept-in from a cobalt-cemented tungsten carbide substrate. In oneembodiment, the first and/or second HPHT process may be performed at apressure of at least about 7.5 GPa. In one embodiment, the infiltrantmay be leached from the infiltrated PCD table using a second acidleaching process following the second HPHT process.

In some embodiments, the pressure employed in the HPHT process used tofabricate the PDC 300 may be sufficient to reduce residual stresses inthe PCD table 304 that develop during the HPHT process due to thethermal expansion mismatch between the substrate 302 and the PCD table304. In such an embodiment, the principal stress measured on the workingsurface 306 of the PDC 300 may exhibit a value of about −345 MPa toabout 0 MPa, such as about −289 MPa. For example, the principal stressmeasured on the working surface 306 may exhibit a value of about −345MPa to about 0 MPa. A conventional PDC fabricated using an HPHT processat a pressure below about 7.5 GPa may result in a PCD table thereofexhibiting a principal stress on a working surface thereof of about−1724 MPa to about −414 MPa, such as about −770 MPa.

Residual stress may be measured on the working surface 306 of the PCDtable 304 of the PDC 300 as described in T. P. Lin, M. Hood, G. A.Cooper, and R. H. Smith, “Residual stresses in polycrystalline diamondcompacts,” J. Am. Ceram. Soc. 77, 6, 1562-1568 (1994). Moreparticularly, residual strain may be measured with a rosette strain gagebonded to the working surface 306. Such strain may be measured fordifferent levels of removal of the substrate 302 (e.g., as material isremoved from the back of the substrate 302). Residual stress may becalculated from the measured residual strain data.

FIG. 3B is a graph of residual principal stress versus substratethickness that was measured in a PCD table of a PDC fabricated atpressure above about 7.5 GPa in accordance with an embodiment of theinvention and a PCD table of a conventionally formed PDC. The residualprincipal stress was determined using the technique described in thearticle referenced above by Lin et al. Curve 310 shows the measuredresidual principal stress on a working surface of the PDC fabricated ata pressure above about 7.5 GPa. The PDC that was fabricated at apressure above about 7.5 GPa had a thickness dimension of about 1 mm andthe substrate had a thickness dimension of about 7 mm and a diameter ofabout 13 mm. Curve 312 shows the measured residual principal stress on aworking surface of a PCD table of a conventionally PDC fabricated atpressure below about 7.5 GPa. The PDC that was fabricated at a pressurebelow about 7.5 GPa had a thickness dimension of about 1 mm and thesubstrate had a thickness dimension of about 7 mm and a diameter ofabout 13 mm. The highest absolute value of the residual principal stressoccurs with the full substrate length of about 7 mm. As shown by thecurves 310 and 312, increasing the pressure, employed in the HPHTprocess used to fabricate a PDC, above about 7.5 GPa may reduce thehighest absolute value of the principal residual stress in a PCD tablethereof by about 60% relative to a conventionally fabricated PDC. Forexample, at the full substrate length, the absolute value of theprincipal residual stress in the PCD table fabricated at a pressureabove about 7.5 GPa is about 60% less than the absolute value of theprincipal residual stress in the PCD table of the conventionallyfabricated PDC.

The following working examples provide further detail about the magneticproperties of PCD tables of PDCs fabricated in accordance with theprinciples of some of the specific embodiments of the invention. Themagnetic properties of each PCD table listed in Tables I-IV were testedusing a KOERZIMAT CS 1.096 instrument that is commercially availablefrom Foerster Instruments of Pittsburgh, Pa. The specific magneticsaturation of each PCD table was measured in accordance with ASTMB886-03 (2008) and the coercivity of each PCD table was measured usingASTM B887-03 (2008) e1 using a KOERZIMAT CS 1.096 instrument. The amountof cobalt-based metal-solvent catalyst in the tested PCD tables wasdetermined using energy dispersive spectroscopy and Rutherfordbackscattering spectroscopy. The specific magnetic saturation constantof the cobalt-based metal-solvent catalyst in the tested PCD tables wasdetermined to be about 201 G·cm³/g using an iterative analysis aspreviously described. When a value of 201 G·cm³/g was used for thespecific magnetic saturation constant of the cobalt-based metal-solventcatalyst, the calculated amount of the cobalt-based metal-solventcatalyst in the tested PCD tables using the analysis software of theKOERZIMAT CS 1.096 instrument substantially matched the measurementsusing energy dispersive spectroscopy and Rutherford spectroscopy.

Table I below lists PCD tables that were fabricated in accordance withthe principles of certain embodiments of the invention discussed above.Each PCD table was fabricated by placing a mass of diamond particleshaving the listed average diamond particle size adjacent to acobalt-cemented tungsten carbide substrate in a niobium container,placing the container in a high-pressure cell medium, and subjecting thehigh-pressure cell medium and the container therein to an HPHT processusing an HPHT cubic press to form a PCD table bonded to the substrate.The surface area of each anvil of the HPHT press and the hydraulic linepressure used to drive the anvils were selected so that the sinteringpressure was at least about 7.8 GPa. The temperature of the HPHT processwas about 1400° C. and the sintering pressure was at least about 7.8GPa. The sintering pressures listed in Table I refer to the pressure inthe high-pressure cell medium at room temperature, and the actualsintering pressures at the sintering temperature are believed to begreater. After the HPHT process, the PCD table was removed from thesubstrate by grinding away the substrate. However, the substrate mayalso be removed using electro-discharge machining or another suitablemethod.

TABLE I Selected Magnetic Properties of PCD Tables Fabricated Accordingto Embodiments of the Invention Average Specific Specific DiamondMagnetic Calcu- Perme- Particle Sintering Saturation lated ability SizePressure (G · cm³/ Co Coercivity (G · cm³/ (μm) (GPa) g) wt % (Oe) g ·Oe) 1 20 7.8 11.15 5.549 130.2 0.08564 2 19 7.8 11.64 5.792 170.00.06847 3 19 7.8 11.85 5.899 157.9 0.07505 4 19 7.8 11.15 5.550 170.90.06524 5 19 7.8 11.43 5.689 163.6 0.06987 6 19 7.8 10.67 5.150 146.90.07263 7 19 7.8 10.76 5.357 152.3 0.07065 8 19 7.8 10.22 5.087 145.20.07039 9 19 7.8 10.12 5.041 156.6 0.06462 10 19 7.8 10.72 5.549 137.10.07819 11 11 7.8 12.52 6.229 135.3 0.09254 12 11 7.8 12.78 6.362 130.50.09793 13 11 7.8 12.69 6.315 134.6 0.09428 14 11 7.8 13.20 6.569 131.60.1003

Table II below lists conventional PCD tables that were fabricated. EachPCD table listed in Table II was fabricated by placing a mass of diamondparticles having the listed average diamond particle size adjacent to acobalt-cemented tungsten carbide substrate in a niobium container,placing the container in a high-pressure cell medium, and subjecting thehigh-pressure cell medium and the container therein to an HPHT processusing an HPHT cubic press to form a PCD table bonded to the substrate.The surface area of each anvil of the HPHT press and the hydraulic linepressure used to drive the anvils were selected so that the sinteringpressure was about 4.6 GPa. Except for samples 15, 16, 18, and 19, whichwere subjected to a temperature of about 1430° C., the temperature ofthe HPHT process was about 1400° C. and the sintering pressure was about4.6 GPa. The sintering pressures listed in Table II refer to thepressure in the high-pressure cell medium at room temperature. After theHPHT process, the PCD table was removed from the cobalt-cementedtungsten carbide substrate by grinding away the cobalt-cemented tungstencarbide substrate.

TABLE II Selected Magnetic Properties of Several Conventional PCD TablesAverage Specific Specific Diamond Magnetic Calcu- Perme- ParticleSintering Saturation lated ability Size Pressure (G · cm³/ Co Coercivity(G · cm³/ (μm) (GPa) g) wt % (Oe) g · Oe) 15 20 4.61 19.30 9.605 94.640.2039 16 20 4.61 19.52 9.712 96.75 0.2018 17 20 4.61 19.87 9.889 94.600.2100 18 20 5.08 18.61 9.260 94.94 0.1960 19 20 5.08 18.21 9.061 100.40.1814 20 20 5.86 16.97 8.452 108.3 0.1567 21 20 4.61 17.17 8.543 102.00.1683 22 20 4.61 17.57 8.745 104.9 0.1675 23 20 5.08 16.10 8.014 111.20.1448 24 20 5.08 16.79 8.357 107.1 0.1568

As shown in Tables I and II, the conventional PCD tables listed in TableII exhibit a higher cobalt content therein than the PCD tables listed inTable I as indicated by the relatively higher specific magneticsaturation values. Additionally, the conventional PCD tables listed inTable II exhibit a lower coercivity indicative of a relatively greatermean free path between diamond grains, and thus may indicate relativelyless diamond-to-diamond bonding between the diamond grains. Thus, thePCD tables according to examples of the invention listed in Table I mayexhibit significantly less cobalt therein and a lower mean free pathbetween diamond grains than the PCD tables listed in Table II.

Table III below lists conventional PCD tables that were obtained fromPDCs. Each PCD table listed in Table III was separated from acobalt-cemented tungsten carbide substrate bonded thereto by grinding.

TABLE III Selected Magnetic Properties of Several Conventional PCDTables Specific Magnetic Specific Saturation Calculated CoercivityPermeability (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 25 17.23 8.572140.4 0.1227 26 16.06 7.991 150.2 0.1069 27 15.19 7.560 146.1 0.1040 2817.30 8.610 143.2 0.1208 29 17.13 8.523 152.1 0.1126 30 17.00 8.458142.5 0.1193 31 17.08 8.498 147.2 0.1160 32 16.10 8.011 144.1 0.1117

Table IV below lists conventional PCD tables that were obtained fromPDCs. Each PCD table listed in Table IV was separated from acobalt-cemented tungsten carbide substrate bonded thereto by grindingthe substrate away. Each PCD table listed in Table IV and tested had aleached region from which cobalt was depleted and an unleached region inwhich cobalt is interstitially disposed between bonded diamond grains.The leached region was not removed. However, to determine the specificmagnetic saturation and the coercivity of the unleached region of thePCD table having metal-solvent catalyst occupying interstitial regionstherein, the leached region may be ground away so that only theunleached region of the PCD table remains. It is expected that theleached region causes the specific magnetic saturation to be lower andthe coercivity to be higher than if the leached region was removed andthe unleached region was tested.

TABLE IV Selected Magnetic Properties of Several Conventional LeachedPCD Tables Specific Magnetic Specific Saturation Calculated CoercivityPermeability (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 33 17.12 8.471143.8 0.1191 34 13.62 6.777 137.3 0.09920 35 15.87 7.897 140.1 0.1133 3612.95 6.443 145.5 0.0890 37 13.89 6.914 142.0 0.09782 38 13.96 6.946146.9 0.09503 39 13.67 6.863 133.8 0.1022 40 12.80 6.369 146.3 0.08749

As shown in Tables I, III, and IV, the conventional PCD tables of TablesIII and IV exhibit a higher cobalt content therein than the PCD tableslisted in Table I as indicated by the relatively higher specificmagnetic saturation values. This is believed by the inventors to be aresult of the PCD tables listed in Tables III and IV being formed bysintering diamond particles having a relatively greater percentage offine diamond particles than the diamond particle formulations used tofabricate the PCD tables listed in Table I.

Embodiments of Applications for PCD and PDCs

The disclosed PCD and PDC embodiments may be used in a number ofdifferent applications including, but not limited to, use in a rotarydrill bit (FIGS. 5A and 5B), a thrust-bearing apparatus (FIG. 6), aradial bearing apparatus (FIG. 7), a subterranean drilling system (FIG.8), and a wire-drawing die (FIG. 9). The various applications discussedabove are merely some examples of applications in which the PCD and PDCembodiments may be used. Other applications are contemplated, such asemploying the disclosed PCD and PDC embodiments in friction stir weldingtools.

FIG. 5A is an isometric view and FIG. 5B is a top elevation view of anembodiment of a rotary drill bit 500. The rotary drill bit 500 includesat least one PDC configured according to any of the previously describedPDC embodiments. The rotary drill bit 500 comprises a bit body 502 thatincludes radially and longitudinally extending blades 504 with leadingfaces 506, and a threaded pin connection 508 for connecting the bit body502 to a drilling string. The bit body 502 defines a leading endstructure for drilling into a subterranean formation by rotation about alongitudinal axis 510 and application of weight-on-bit. At least one PDCcutting element, configured according to any of the previously describedPDC embodiments (e.g., the PDC 300 shown in FIG. 3A), may be affixed tothe bit body 502. With reference to FIG. 5B, a plurality of PDCs 512 aresecured to the blades 504. For example, each PDC 512 may include a PCDtable 514 bonded to a substrate 516. More generally, the PDCs 512 maycomprise any PDC disclosed herein, without limitation. In addition, ifdesired, in some embodiments, a number of the PDCs 512 may beconventional in construction. Also, circumferentially adjacent blades504 define so-called junk slots 518 therebetween, as known in the art.Additionally, the rotary drill bit 500 may include a plurality of nozzlecavities 520 for communicating drilling fluid from the interior of therotary drill bit 500 to the PDCs 512.

FIGS. 5A and 5B merely depict an embodiment of a rotary drill bit thatemploys at least one cutting element comprising a PDC fabricated andstructured in accordance with the disclosed embodiments, withoutlimitation. The rotary drill bit 500 is used to represent any number ofearth-boring tools or drilling tools, including, for example, core bits,roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits,reamers, reamer wings, or any other downhole tool including PDCs,without limitation.

The PCD and/or PDCs disclosed herein (e.g., the PDC 300 shown in FIG.3A) may also be utilized in applications other than rotary drill bits.For example, the disclosed PDC embodiments may be used in thrust-bearingassemblies, radial bearing assemblies, wire-drawing dies, artificialjoints, machining elements, and heat sinks.

FIG. 6 is an isometric cut-away view of an embodiment of athrust-bearing apparatus 600, which may utilize any of the disclosed PDCembodiments as bearing elements. The thrust-bearing apparatus 600includes respective thrust-bearing assemblies 602. Each thrust-bearingassembly 602 includes an annular support ring 604 that may be fabricatedfrom a material, such as carbon steel, stainless steel, or anothersuitable material. Each support ring 604 includes a plurality ofrecesses (not labeled) that receive a corresponding bearing element 606.Each bearing element 606 may be mounted to a corresponding support ring604 within a corresponding recess by brazing, press-fitting, usingfasteners, or another suitable mounting technique. One or more, or allof bearing elements 606 may be configured according to any of thedisclosed PDC embodiments. For example, each bearing element 606 mayinclude a substrate 608 and a PCD table 610, with the PCD table 610including a bearing surface 612.

In use, the bearing surfaces 612 of one of the thrust-bearing assemblies602 bear against the opposing bearing surfaces 612 of the other one ofthe bearing assemblies 602. For example, one of the thrust-bearingassemblies 602 may be operably coupled to a shaft to rotate therewithand may be termed a “rotor.” The other one of the thrust-bearingassemblies 602 may be held stationary and may be termed a “stator.”

FIG. 7 is an isometric cut-away view of an embodiment of a radialbearing apparatus 700, which may utilize any of the disclosed PDCembodiments as bearing elements. The radial bearing apparatus 700includes an inner race 702 positioned generally within an outer race704. The outer race 704 includes a plurality of bearing elements 706affixed thereto that have respective bearing surfaces 708. The innerrace 702 also includes a plurality of bearing elements 710 affixedthereto that have respective bearing surfaces 712. One or more, or allof the bearing elements 706 and 710 may be configured according to anyof the PDC embodiments disclosed herein. The inner race 702 ispositioned generally within the outer race 704, and thus the inner race702 and outer race 704 may be configured so that the bearing surfaces708 and 712 may at least partially contact one another and move relativeto each other as the inner race 702 and outer race 704 rotate relativeto each other during use.

The radial bearing apparatus 700 may be employed in a variety ofmechanical applications. For example, so-called “roller-cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 702 may be mounted to a spindle of aroller cone and the outer race 704 may be mounted to an inner boreformed within a cone and such an outer race 704 and inner race 702 maybe assembled to form a radial bearing apparatus.

Referring to FIG. 8, the thrust-bearing apparatus 600 and/or radialbearing apparatus 700 may be incorporated in a subterranean drillingsystem. FIG. 8 is a schematic isometric cut-away view of a subterraneandrilling system 800 that includes at least one of the thrust-bearingapparatuses 600 shown in FIG. 6 according to another embodiment. Thesubterranean drilling system 800 includes a housing 802 enclosing adownhole drilling motor 804 (i.e., a motor, turbine, or any other devicecapable of rotating an output shaft) that is operably connected to anoutput shaft 806. A first thrust-bearing apparatus 600 ₁ (FIG. 6) isoperably coupled to the downhole drilling motor 804. A secondthrust-bearing apparatus 600 ₂ (FIG. 6) is operably coupled to theoutput shaft 806. A rotary drill bit 808 configured to engage asubterranean formation and drill a borehole is connected to the outputshaft 806. The rotary drill bit 808 is shown as a roller-cone bitincluding a plurality of roller cones 810. However, other embodimentsmay utilize different types of rotary drill bits, such as a so-called“fixed-cutter” drill bit shown in FIGS. 5A and 5B. As the borehole isdrilled, pipe sections may be connected to the subterranean drillingsystem 800 to form a drill string capable of progressively drilling theborehole to a greater depth within the earth.

A first one of the thrust-bearing assemblies 602 of the thrust-bearingapparatus 600 ₁ is configured as a stator that does not rotate and asecond one of the thrust-bearing assemblies 602 of the thrust-bearingapparatus 600 ₁ is configured as a rotor that is attached to the outputshaft 806 and rotates with the output shaft 806. The on-bottom thrustgenerated when the drill bit 808 engages the bottom of the borehole maybe carried, at least in part, by the first thrust-bearing apparatus 600₁. A first one of the thrust-bearing assemblies 602 of thethrust-bearing apparatus 600 ₂ is configured as a stator that does notrotate and a second one of the thrust-bearing assemblies 602 of thethrust-bearing apparatus 600 ₂ is configured as a rotor that is attachedto the output shaft 806 and rotates with the output shaft 806. Fluidflow through the power section of the downhole drilling motor 804 maycause what is commonly referred to as “off-bottom thrust,” which may becarried, at least in part, by the second thrust-bearing apparatus 600 ₂.

In operation, drilling fluid may be circulated through the downholedrilling motor 804 to generate torque and effect rotation of the outputshaft 806 and the rotary drill bit 808 attached thereto so that aborehole may be drilled. A portion of the drilling fluid may also beused to lubricate opposing bearing surfaces of the bearing elements 606of the thrust-bearing assemblies 602.

FIG. 9 is a side cross-sectional view of an embodiment of a wire-drawingdie 900 that employs a PDC 902 fabricated in accordance with theteachings described herein. The PDC 902 includes an inner, annular PCDregion 904 comprising any of the PCD tables described herein that isbonded to an outer cylindrical substrate 906 that may be made from thesame materials as the substrate 302 shown in FIG. 3A. The PCD region 904also includes a die cavity 908 formed therethrough configured forreceiving and shaping a wire being drawn. The wire-drawing die 900 maybe encased in a housing (e.g., a stainless steel housing), which is notshown, to allow for handling.

In use, a wire 910 of a diameter “d₁” is drawn through die cavity 908along a wire-drawing axis 912 to reduce the diameter of the wire 910 toa reduced diameter “d₂.”

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall have the same meaning as the word“comprising” and variants thereof (e.g., “comprise” and “comprises”).

The invention claimed is:
 1. A method of characterizing polycrystallinediamond, the method comprising: providing a polycrystalline diamondcompact including a polycrystalline diamond table bonded to a substrate,the polycrystalline diamond table including a plurality of diamondgrains defining a plurality of interstitial regions, at least a portionof the plurality of interstitial regions being occupied by a metallicmaterial; separating the polycrystalline diamond table from thesubstrate; and after the act of separating the polycrystalline diamondtable from the substrate, measuring at least one magnetic characteristicof the polycrystalline diamond table.
 2. The method of claim 1 whereinmeasuring at least one magnetic characteristic of the polycrystallinediamond table comprises measuring a coercivity of the polycrystallinediamond table.
 3. The method of claim 1 wherein measuring at least onemagnetic characteristic of the polycrystalline diamond table comprisesmeasuring a magnetic saturation of the polycrystalline diamond table. 4.The method of claim 1 wherein measuring at least one magneticcharacteristic of the polycrystalline diamond table comprises measuringa coercivity of the polycrystalline diamond table.
 5. The method ofclaim 1 wherein measuring at least one magnetic characteristic of thepolycrystalline diamond table comprises measuring a coercivity of thepolycrystalline diamond table.
 6. The method of claim 1 whereinmeasuring at least one magnetic characteristic of the polycrystallinediamond table comprises measuring a magnetic saturation of thepolycrystalline diamond table.
 7. The method of claim 1, furthercomprising: wherein measuring at least one magnetic characteristic ofthe polycrystalline diamond table comprises measuring a magneticsaturation and a coercivity of the polycrystalline diamond table; anddetermining a specific permeability of the polycrystalline diamond tablebased on the magnetic saturation and the coercivity.
 8. The method ofclaim 1, further comprising: wherein measuring at least one magneticcharacteristic of the polycrystalline diamond table comprises measuringa magnetic saturation of the polycrystalline diamond table; anddetermining a specific magnetic saturation of the polycrystallinediamond table at least partially based on the magnetic saturation and amass of the polycrystalline diamond table.
 9. The method of claim 1,further comprising: wherein measuring at least one magneticcharacteristic of the polycrystalline diamond table comprises measuringa magnetic saturation of the polycrystalline diamond table; anddetermining a concentration of the metallic material at least partiallybased on the at least one magnetic characteristic.
 10. The method ofclaim 1, further comprising determining a concentration of the metallicmaterial at least partially based on the at least one magneticcharacteristic.
 11. The method of claim 1 wherein the metallic materialcomprises a metal-solvent catalyst.
 12. The method of claim 11 whereinthe metal-solvent catalyst comprises a member selected from the groupconsisting of iron, nickel, cobalt, and alloys thereof.
 13. The methodof claim 1, further comprising calculating a concentration of themetallic material at least partially based on the at least one magneticcharacteristic.
 14. The method of claim 1 wherein the polycrystallinediamond table is un-leached.
 15. The method of claim 1 whereinseparating the polycrystalline diamond table from the substratecomprises grinding the substrate or removing the substrate from thepolycrystalline diamond table by electro-discharge machining.
 16. Themethod of claim 1, further comprising determining at least one physicalcharacteristic of the polycrystalline diamond table at least partiallybased on the at least one magnetic characteristic.
 17. A method,comprising: providing a polycrystalline diamond compact including apolycrystalline diamond table bonded to a substrate, the polycrystallinediamond table including a plurality of diamond grains defining aplurality of interstitial regions, the polycrystalline diamond tablefurther including a leached region remote from the substrate and anun-leached region adjacent to the substrate; separating the unleachedregion of the polycrystalline diamond table from the substrate and theleached region; and measuring at least one magnetic characteristic ofthe unleached region of the polycrystalline diamond table.
 18. Themethod of claim 17, further comprising determining at least one physicalcharacteristic of the unleached region of the polycrystalline diamondtable at least partially based on the at least one magneticcharacteristic.
 19. The method of claim 17 wherein measuring at leastone magnetic characteristic of the unleached region of thepolycrystalline diamond table comprises measuring at least one of amagnetic saturation or a coercivity of the un-leached region of thepolycrystalline diamond table.